(Reuters) - PresidentHassan Rouhani said on Tuesday international sanctions on Iran would unravel in months following negotiations with world powers on its nuclear program, the official IRNA news agency reported.

Some international sanctions imposed over Iran's nuclear program have been eased temporarily after a deal was reached last year with world powers, but Washington has said the lifting of sanctions can only happen "in total" after a comprehensive deal is reached.

"With your support, this government has taken the first steps towards the lifting of the brutal sanctions ... We will witness the sanctions shattering in the coming months," Rouhani told a crowd during a tour of Sistan-Baluchestan, a restive underdeveloped province bordering Pakistan.

"Today we already see the sanctions unraveling," he said, according to IRNA, referring to the modest easing of sanctions in return for concessions made by Rouhani's government in nuclear talks with world powers.

World powers want Iran to curb its nuclear activity, which Western nations fear is aimed at giving Tehran the capability to make a nuclear weapon. Iran denies that, saying its nuclear program is only for power generation and civilian uses.

The sanctions have bitten deeply. In late 2012, Iran's economy was losing billions of dollars per month as sanctions slashed oil sales. Its currency plunged, inflation jumped and the economy went into recession.

In an interim deal with Iran reached in November, U.S. and E.U. negotiators agreed to lift sanctions on sectors such as petrochemicals and precious metals for six months, with broader sanctions relief if Iran agrees to permanent curbs on its nuclear program.

The president blamed both the sanctions and "tactless policies" by the previous hardline administration of Mahmoud Ahmadinejad for the economic hardship faced by his nation.

"Due to the brutal sanctions and unwise administration, our country has faced myriad problems in the past years... but we will break down the inhuman sanctions," Rouhani said.

"We will prove to the world through these negotiations that what has been said about Iran is a lie. Iran has never pursued nuclear weapons and never will."

Western powers, along with Russia and China, want to prevent tensions in the Middle East from boiling over into a wider war or triggering a regional nuclear arms race.

Iran exported oil at levels higher than allowed under the sanctions for a fourth straight month in February, ship loading data seen by Reuters showed, raising the risk of a crackdown if Washington feels economic pressure is being relaxed too quickly. Iran's main clients are mostly in Asia.